High-strength beryllium-free moulded body made from zirconium alloys which may be plastically deformed at room temperature

ABSTRACT

High-strength, beryllium-free moulded bodies made from zirconium alloys which may be plastically deformed comprise a material essentially corresponding to the following formula in composition: Zr a (E1) b (E2) c (E3) d (E4) e , where E1=one or several of Nb, Ta, Mo, Cr, W, Ti, V, Hf and Y, E2=one or several of Cu, Au, Ag, Pd and Pt, E3=one or several of Ni, Co, Fe, Zn and Mn, E4=one or several of AI, Ga, Si, P, C, B, Sn, Pb and Sb, a=100−(b+c+d+e), b=5 to 15, c=5 to 15, d=0 to 15 and e=5 to 15 (a, b, c d, e in atom %). The moulded body essentially comprises a homogeneous, microstructural structure which is a glass-like or nano-crystalline matrix with a ductile, dendritic, cubic body-centred phase embedded therein.

[0001] The invention relates to high-strength, beryllium-free, moldedzirconium alloy objects which are plastically deformable at roomtemperature.

[0002] Such molded objects can be used as high-stressed components, forexample, in the aircraft industry, in space travel and also in theautomobile industry, but also for medical equipment and implants in themedical area, when the mechanical load-carrying capability, thecorrosion resistance and the surface stresses must satisfy highrequirements, especially in the case of components having a complicatedshape.

[0003] It is well known that certain multicomponent, metallic materialscan be transformed into a metastable, glassy state (metallic glasses) byrapid solidification, in order to obtain advantageous properties, suchas soft magnetic, mechanical and/or catalytic properties. Because of thecooling rate required for the melt, most of these materials can beproduced only with small dimensions in at least one direction, forexample, as thin strips or powders. With that, they are unsuitable assolid construction materials (see, for example, B. T. Masumoto, Mater.Sci. Eng. A179/180 (1994) 8-16).

[0004] Furthermore, certain compositional ranges of multi-componentalloys are known in which such metallic glasses can also be produced insolid form, for example, with dimensions greater then 1 mm, by castingprocesses. Such alloys are, for example, Pd—Cu—Si,Pd₄₀Ni₄₀P₂₀,Zn—Cu—Ni—Al, La—Al—Ni—Cu (see, for example, B. T. Masumoto,Mater. Sci. Eng. A179/180 (1994) 8-16 and W. L. Johnson in Mater. Sci.Forum Vol. 225-227, pages 35-50, Transtec Publications 1996,Switzerland).

[0005] Especially, beryllium-containing metallic glasses, which have acomposition corresponding to the chemical formula(Zr_(1-x)Ti_(x))_(a1)ETM_(a2)(Cu_(1-y)Ni_(y))_(b1)LTM_(b2)Be_(c), anddimensions greater than 1 mm, are also known (A. Peker, W. L. Johnson,U.S. Pat. No. 5,288,344). In this connection, the coefficient a1, a2,b1, b2, c, x, y refer to the content of the elements in atom percent,ETM is an early transition metal and LTM a late transition metal.

[0006] Furthermore, molded metallic glass objects, larger than 1 mm inall their dimensions, are known for certain composition rangers of thequinary Zr—Ti—Al—Cu—Ni alloys (L. Q. Xing et al. Non-Cryst. Sol 205-207(1996) p. 579-601, presented at 9^(th) Int. Conf. on Liquid andAmorphous Metals, Chicago, Aug, 27 to Sep. 1, 1995; Xing et al., Mater.Sci. Eng. A 220 (1996) 155-161) and the pseudoquinary alloy (Zr,Hf)_(a)(Al, Zn)_(b)(Ti, Nb)_(c)(Cu_(x)Fe_(y)(Ni, Co)_(z))_(d) (DE 197 06768 06 768 A1; DE 198 33 329 C2).

[0007] A composition of a multi-component beryllium-containing alloywith the chemical formula(Zr_(100-a-b)Ti_(a)Nb_(b))₇₅(Be_(x)Cu_(y)Ni_(z))₂₅ is also known. Inthis connection, the coefficients a and b refer to the proportion of theelements in atom percent with a=18.34 and b=6.66 and the coefficients x,y and z refer to the ratio in atom percent with x:y:z=9:5:4. This is atwo-phase alloy; it has a brittle, glassy matrix of high strength and aductile, plastically deformable, dendritic, cubic, body centered phase.As a result, there is an appreciable improvement in the mechanicalproperties at room temperature, particularly in the area of microscopicexpansion (C. C. Hays, C. P. Kim and W. L. Johnson, Phys. Rev. Lett. 84,13, p. 2901-2904 (2000)). However, the use of the highly toxic berylliumis a serious disadvantage of this alloy.

[0008] It is an object of the invention to make a beryllium-free, highstrength, and plastically deformable, molded objects of zirconium alloysavailable which, in comparison to the aforementioned metallic glasses,have macroscopic plasticity and deformation consolidation during shapingprocesses at room temperature, without a significant effect on otherproperties such as strength, elastic expansion or corrosion behavior.

[0009] This objective is accomplished by the high-strength moldedobjects given in the claims.

[0010] The inventive molded objects are characterized in that theyconsist of a material, the composition of which corresponds to theformula:

Zr_(a)(E1)_(b)(E2)_(c)(E3)_(d)(E4)_(e)

[0011] in which:

[0012] E1 consists of an element or several elements of the group formedby the elements Nb, Ta, Mo, Cr, W, Ti, V, Hf, and Y,

[0013] E2 consists of an element or several element of the group formedby the elements Cu, Au, Ag, Pd and Pt,

[0014] E3 consists of an element or several element of the group formedby the elements Ni, Co, Fe, Zn and Mn, and

[0015] E4 consists of an element or several element of the group formedby the elements Al, Ga, Si, P, C, B, Sn, Pb and Sb;

[0016] with:

[0017] a=100−(b+c+d+e)

[0018] b=5 to 15

[0019] c=5 to 15

[0020] d=0 to 15

[0021] e=5 to 15

[0022] (a, b, c, d, e in atom percent)

[0023] and optionally with small additions and impurities as required bythe manufacturing process.

[0024] A further characterizing, distinguishing feature consists thereinthat the molded objects have a homogenous, microstructural structure,which consists of a glassy nanocrystalline matrix, in which a ductile,dendritic, cubic, body-centered phase is embedded, a third phasepossible being contained in a proportion by volume not exceeding 10percent.

[0025] It is advantageous if the material contains the element Nb as E1,the element Cu as E2, the element Ni as E3 and the element Al as E4.

[0026] In order to realize particularly advantageous properties thematerial should have a composition with b=6 to 10, c=6 to 11, d=0 to 9and e=7 to 12.

[0027] A composition with the ratios of Zr:Nb=5:1 to 11:1 and Zr:Al=6:1to 9:1 is advantageous.

[0028] The dendritic, cubic, body-centered phase, contained in thematerial, should advantageously have a composition with b=7 to 15, c=3to 9, d=0 to 3 and e=7 to 10 (numerical data in atom percent). Amaterial with particular good properties consists ofZr_(66.4)Nb_(6.4)Cu_(10.5)Ni_(8.7)Al₈ (numerical data in atom percent).

[0029] A further material with particular good properties consists ofZr₇₁Nb₉Cu₈Ni₁Al₁₁ (numerical data in atom percent).

[0030] Pursuant to the invention, the proportion by volume of thedendritic, cubic, body-centered phase, formed in the matrix, is 25 to 95percent and preferably 50 to 95 percent.

[0031] The length of the primary dendritic axes ranges from 1 μm to 100μm and the radius of the primary dendrites is 0.2 μm to 2 μm.

[0032] For preparing the molded object, a semi finished product or thefinished casting is prepared by casting the melted zirconium alloy intoa copper mold.

[0033] The detection of the dendritic, cubic, body-centered phase in theglassy or nanocrystalline matrix and the determination of the size andproportion by volume of the dendritic precipitates can be made by x-raydiffraction, scanning electron microscopy or transmission electronmicroscopy.

[0034] The invention is explained in greater detail below by means ofexamples.

EXAMPLE 1

[0035] An alloy, having the composition Zr₇₁Nb₉Cu₈Ni₁Al₁₁ (numericaldata in atom percent) is cast in a cylindrical copper mold having aninternal diameter of 5 mm. The molded object obtained consists of aglass-like matrix in which a ductile, cubic, body-centered phase isembedded. The proportion by volume of the dendritic phase is about 50%.By these means, an elongation at break of 3.5% at a breaking strength of1791 MPa is achieved. The elastic elongation at the technical yieldpoint (0.2% yield strength) is 2.5% at a strength of 1638 MPa. Themodulus of elasticity is 72 GPa.

EXAMPLE 2

[0036] An alloy, having the composition Zr₇₁Nb₉Cu₈Ni₁Al₁₁, (numericaldata in atom percent) is cast in a cylindrical copper mold having aninternal diameter of 3 mm. The molded object obtained consists of ananocrystalline matrix in which a ductile, cubic, body-centered phase isembedded. The proportion by volume of the dendritic phase is about 95%.By these means, an elongation at break of 5.4% at a breaking strength of1845 MPa is achieved. The elastic elongation at the technical yieldpoint (0.2% yield strength) is 1.5% at a strength of 1440 MPa. Themodulus of elasticity is 108 GPa.

EXAMPLE 3

[0037] An alloy, having the compositionZr_(66.4)Nb_(4.4)Mo₂Cu_(10.5)Ni_(8.7)Al₈(numerical data in atom percent)is cast in a cylindrical copper mold having an internal diameter of 5mm. The molded object obtained consists of a glass-like matrix in whicha ductile, cubic, body-centered phase is embedded. The proportion byvolume of the dendritic phase is about 50 percent. By these means, anelongation at break of 3.4% at a breaking strength of 1909 MPa isachieved. The elastic elongation at the technical yield point (0.2percent yield strength) is 2.1% at a strength of 1762 MPa. The modulusof elasticity is 94 GPa.

EXAMPLE 4

[0038] An alloy, having the composition Zr₇₀Nb_(10.5)Cu₈Ni₂Al_(9.5)(numerical data in atom percent) is cast in a cylindrical copper moldhaving an internal diameter of 3 mm. The molded object obtained consistsof a nanocrystalline matrix in which ductile, cubic, body-centered phaseis embedded. The proportion by volume of the dendritic phase is about 95percent. By these means, an elongation at break of 6.2% at a breakingstrength of 1680 MPa is achieved. The elastic elongation at thetechnical yield point (0.2% yield strength) is 1.9% at a strength of1401 MPa. The modulus of elasticity is 84 GPa.

What we claim is:
 1. High strength, beryllium-free, molded zirconiumalloy objects, which are plastically deformable at room temperature,wherein the molded objects comprise a material, the composition of whichcorresponds to the formula: Zr_(a)(E1)_(b)(E2)_(c)(E3)_(d)(E4)_(e) inwhich: E1 is an element or several elements of the group formed by theelements Nb, Ta, Mo, Cr, W, Ti, V, Hf, and Y, E2 an element or severalelement of the group formed by the elements Cu, Au, Ag, Pd and Pt, E3 isan element or several element of the group formed by the elements Ni,Co, Fe, Zn and Mn, and E4 is an element or several element of the groupformed by the elements Al, Ga, Si, P, C, B, Sn, Pb and Sb; with:a=100−(b+c+d+e) b=5 to 15 c=5 to 15 d=0 to 15 e=5 to 15 (a, b, c, d, ein atom percent) and optionally with small additions and impurities asrequired by the manufacturing process, and that the molded objects havea homogenous, microstructural structure, which comprises a glassynanocrystalline matrix, in which a ductile, dendritic, cubic,body-centered phase is embedded, a third phase possible being containedin a proportion by volume not exceeding 10 percent.
 2. The moldedobjects of claim 1, in which the material preferably contains theelement Nb as E1, the element Cu as E2, the element Ni as E3 and theelement Al as E4.
 3. The molded objects of claim 1, wherein the materialhas a composition with b=6 to 10, c=6 to 11, d=0 to 9 and e=7 to
 12. 4.The molded objects of claim 1, wherein the material has a compositionwith the rations of b=6 to 10, c=6 to 11, d=0 to 9 and e=7 to
 12. 5. Themolded objects of claim 1, wherein the dendritic, cubic, body-centeredphase contained in the material has a composition with b=7 to 15, c=3 to9, d=0 to 3 and e=7 to
 10. 6. The molded objects of claim 1, wherein thematerial is Zr_(66.4)Nb_(6.4)Cu_(10.5)Ni_(8.7)Al₈ (numerical in atompercent).
 7. The molded objects of claim 1, wherein the material isZr₇₁Nb₉Cu₈Ni₁Al₁₁ (numerical data in atom percent.)
 8. The moldedobjects of claim 1, wherein the proportion by volume of the dendritic,cubic, body-centered phased, formed in the matrix is 25 percent to 95percent and preferably 50 percent to 95 percent.
 9. The molded objectsof claim 1, wherein the length of the primary dendritic axes in thedendritic, cubic, body-entered phase range from 1 μm to 100 μm and theradius of the primary dendrites ranges from 0.2 μm to 2 μm.